1. Field of the Invention
The invention relates to liquid cleaning compositions containing polymeric thickeners and hypochlorite generating bleach.
2. The Prior Art
Polymeric thickeners are often added to liquid products to enhance rheological solution properties including viscosity and yield point. Specifically, the thickeners must meet the properties of water solubility, stability toward hypochlorite oxidation, and retention of viscosity building properties. Special problems arise with the thickeners when the liquid products also contain a hypochlorite bleach.
Cross-linked or pseudo cross-linked polymers have been known as efficient viscosifiers because they form extended networks in solution. These network forming polymers are particularly useful as gelling agents or for suspension of solid particles. Examples of such materials are the natural gums including tragacanth and xanthan. Synthetic cross-linked polymers have been described in numerous patents and been commercially available for many years.
U.S. Pat. No. 2,798,053 (Brown) discloses a water dispersible cross-linked interpolymer of a monomeric polymerizable alpha-beta monoolefinically unsaturated lower aliphatic carboxylic acid with a polyether of a polyol. The polyol is selected from oligosaccharides, reduced derivatives thereof and pentaerythritol, the hydroxyl groups of the polyol being modified with at least two allyl ether groups per molecule. These materials are commercially available from The B. F. Goodrich Company under the trademark of Carbopol.RTM. resins.
U.S. Pat. No. 2,810,716 (Markus et al.) describes acrylic acid polymers cross-linked with poly-unsaturated compounds including trivinyl benzene and 2,5-dimethyl-3,4-dihydroxy-1,5-hexadiene.
U.S. Pat. No. 2,985,625 (Jones) discloses water thickening compositions useful in cleaning products which are insoluble but highly hydrophilic interpolymers. At least three monomers combine to produce these interpolymers. Illustrative of these thickeners are terpolymers combining maleic anhydride, a vinyl alkyl ether or acrylic derivative, and a cross-linking agent with more than one polymerizable olefinic bond. Substances such as polyallyl sucrose, polyallyl pentaerythritol, and polybutadiene (with a plurality of side CH.sub.2 .dbd.CH groups) are suggested as cross-linking agents.
U.S. Pat. No. 4,228,048 (Tesdahl) suggests use of modified polyacrylic acid salt in liquid cleaning compositions containing sodium hypochlorite. Especially preferred is a polyallyl sucrose modified polyacrylic acid salt identified as Carbopol 941.RTM..
A number of patents have reported use of linear sodium polyacrylate in chlorine bleach containing cleaning compositions. Linear polyacrylate was not, however, used for its thickening properties but rather to improve protection of the overglaze layer on fine china. See GB 2 164 350A (Lai et al.) and GB 2 163 447A (Colarusso). In U.S. Pat. No. 4,147,650, sodium polyacrylate was included in a mechanical dishwashing formulation alongside sodium hypochlorite and sodium tripolyphosphate. Polyacrylate was found to extend the water softening properties of the tripolyphosphate. U.S. Pat. No. 3,579,455 (Sabatelli et al.) reports use of a polyacrylate in a dishwashing composition reporting this polymer to be useful for reducing spotting and improving clarity on glassware.
Liquids containing hypochlorite bleach are especially destructive to most synthetic and natural polymers. In fact, only linear polyacrylates have been found to have even marginal stability in solutions containing active chlorine. Furthermore, water-soluble polymers, such as the linear polyacrylates, are often susceptible to phase separation in highly alkaline or high ionic strength aqueous systems.
Those of the aforementioned compositions incorporating non-cross-linked polyacrylate and the like polymers have not suggested that they enhance viscosity; indeed, these linear polymers do not significantly enhance viscosity. Those of the aforementioned patents reporting hypochlorite compositions, such as U.S. Pat. No. 4,228,048, have not addressed the problem of oxidative degradation of the polymer thickener. For instance, Carbopol 941.RTM. is excellent at thickening but has very poor resistance to oxidation.
Currently available naturally derived network-forming polymers are incompatible with hypochlorite. Polysaccharides such as cellulose, xanthan and gum tragacanth, all having numerous hydroxyl groups and either linkages, degrade rapidly in the presence of active chlorine. Commercial synthetic polymers such as Alcogum SL-70.RTM. and Ucar.RTM. resins contain urethane linkages which render these materials susceptible to both degradation and phase separation in high ionic strength, bleach-containing solutions. Carbopol.RTM. resins lose a large portion of their gelforming ability and phase separate after less than one week of hypochlorite contact. Acrysol ICS-1.RTM. and the Acrysol ASE.RTM. resins show similar behavior. Thus, polymeric thickeners are needed which can maintain adequate performance under harsh, long-term storage conditions found with bleach containing household products.
Accordingly, it is an object of the invention to provide a liquid hypochlorite detergent product which is adequately thickened with a polymer.
A further object of the invention is to provide a hypochlorite containing detergent product having a thickening polymer resistant to bleach induced degradation.
A further object of the invention is to provide a liquid or gel type detergent composition useful as an automatic dishwashing product.
A still further objective of the invention is to obtain a polymeric thickener for hypochlorite containing compositions which not only has chemical and physical stability relative to all components but is also soluble in aqueous media.
These and other objects of the present invention will become apparent as further details are provided in the subsequent discussion and Examples.